National Electrical Code (NEC)


The National Electrical Code (NEC), or NFPA 70, is a United States standard for the safe installation of electrical wiring and equipment. It is part of the National Fire Codes series published by the National Fire Protection Association (NFPA). While the NEC is not itself a U.S. law, NEC use is commonly mandated by state or local law, as well as in many jurisdictions outside of the United States. The NEC codifies the requirements for safe electrical installations into a single, standardized source. The "authority having jurisdiction" inspects for compliance with these minimum standards.
The NEC is developed by NFPA's Committee on the National Electrical Code, which consists of 19 code-making panels and a technical correlating committee. Work on the NEC is sponsored by the National Fire Protection Association. The NEC is approved as an American national standard by the American National Standards Institute (ANSI). It is formally identified as ANSI/NFPA 70.
First published in 1897, the NEC is updated and published every three years. The 2008 Code is the most recent edition.  Although the code is updated every three years, some jurisdictions do not immediately adopt the new edition.
The NEC covers the installation of electrical conductors, equipment, and raceways; signaling and communications conductors, equipment, and raceways; and optical fiber cables and raceways for the following:
  1. Public and private premises, including buildings, structures, mobile homes, recreational vehicles, and floating buildings
  2. Yards, lots, parking lots, carnivals, and industrial substations
  3. Installations of conductors and equipment that connect to the supply of electricity
  4. Installations used by the electric utility, such as office buildings, warehouses, garages, machine shops, and recreational buildings, that are not an integral part of a generating plant, substation, or control center.
The NEC is composed of an introduction, nine chapters, annexes A through H, and the index. The introduction sets forth the purpose, scope, enforcement and rules or information that are general in nature.
The first four chapters cover definitions and rules for installations (voltages, connections, markings, etc), circuits and circuit protection, methods and materials for wiring (wiring devices, conductors, cables, etc), and general-purpose equipment (cords, receptacles, switches, heaters, etc).
The next three chapters deal with special occupancies (high risk to multiple persons), special equipment (signs, machinery, etc) and special conditions (emergency systems, alarms, etc).
Chapter 8 is specific to additional requirements for communications systems (telephone, radio/TV, etc) and chapter 9 is composed of ten tables regarding conductor, cable and conduit properties, among other things.
Annexes A-G relate to referenced standards, calculations, examples, additional tables for proper implementation of various code articles (e.g., how many wires fit in a conduit) and a model adoption ordinance.
"National Electrical Code" and "NEC" are registered trademarks of the NFPA.
For more information about the NEC, please visit the website of the National Fire Protection Association at